test(profiles): pin projects/tree single-flight as a behaviour contract

Replace the attribute-presence check (asserts a cache_clear attribute the decorator does not
expose) with one invariant: eight concurrent projects/tree requests run the profile scan once
and each caller gets its own copy of the payload. The scope-suite fixture now disables the TTL
instead of calling a non-existent clear hook, which silently no-op'd.

tests/hermes_cli/test_profiles_sidebar_cache.py

@@ -172,20 +172,37 @@ class SidebarCacheTests(unittest.TestCase):
 
         self.assertEqual(inspect.signature(wrapped), inspect.signature(scan))
 
-    def test_heavy_sidebar_endpoints_are_all_single_flight_wrapped(self):
-        # HostHighCPU on a 2-vCore box: /api/profiles/projects/tree was the
-        # one heavy sidebar endpoint left uncoalesced, so every Desktop poll
-        # re-ran the full 50-profile fan-out. Any new heavy sidebar endpoint
-        # must carry the wrapper too — this pins the existing two.
-        for endpoint in (
-            profiles.get_profiles_sessions_sidebar,
-            profiles.get_profiles_projects_tree,
-        ):
-            self.assertTrue(
-                callable(getattr(endpoint, "cache_clear", None)),
-                f"{endpoint.__name__} lost its @_sidebar_singleflight_cache "
-                "wrapper — concurrent Desktop polls will re-scan every profile",
-            )
+    def test_projects_tree_coalesces_concurrent_scans_and_returns_copies(self):
+        # /api/profiles/projects/tree fans out over every profile's state.db; desktop
+        # background sync + sidebar refreshes overlap identical requests. One scan must
+        # serve the whole burst, and no two callers may share the same payload object.
+        workers = 8
+        entered = threading.Event()
+        release = threading.Event()
+        scans = 0
+        scans_lock = threading.Lock()
+
+        def fake_read(name, home, errors, fn):
+            nonlocal scans
+            with scans_lock:
+                scans += 1
+            entered.set()
+            self.assertTrue(release.wait(timeout=2))
+            return None
+
+        with mock.patch.object(profiles, "_profile_targets", return_value=[("default", Path("/nonexistent"))]), \
+                mock.patch.object(profiles, "_read_profile_db", side_effect=fake_read), \
+                ThreadPoolExecutor(max_workers=workers) as pool:
+            futures = [pool.submit(profiles.get_profiles_projects_tree) for _ in range(workers)]
+            self.assertTrue(entered.wait(timeout=1))
+            time.sleep(0.05)
+            release.set()
+            results = [future.result(timeout=2) for future in futures]
+
+        self.assertEqual(scans, 1)
+        self.assertEqual(len({id(r) for r in results}), workers)
+        self.assertEqual(results, [results[0]] * workers)
+        self.assertEqual(results[0]["projects"], [])
 
 
 if __name__ == "__main__":

tests/hermes_cli/test_profiles_sidebar_scope.py

@@ -15,30 +15,13 @@ import pytest
 
 
 @pytest.fixture(autouse=True)
-def _cold_sidebar_singleflight_caches():
-    """Force a cold single-flight cache around every test in this file.
-
-    Both sidebar endpoints are wrapped in ``_sidebar_singleflight_cache``
-    (5s TTL). Each test builds a fresh tmp profile set, so a warm entry from
-    a previous test — same default query params, different disk state — would
-    answer with another test's payload. Clearing before and after keeps every
-    request cold without disabling the caching the endpoints rely on.
-    """
+def _uncached_sidebar_endpoints(monkeypatch):
+    """Both sidebar endpoints sit behind ``_sidebar_singleflight_cache`` (5s TTL). Every
+    test here builds a fresh tmp profile set under the same default query params, so a warm
+    entry would answer with another test's payload. TTL 0 makes each request cold."""
     from hermes_cli.web_routers import profiles as profiles_routes
 
-    endpoints = (
-        profiles_routes.get_profiles_sessions_sidebar,
-        profiles_routes.get_profiles_projects_tree,
-    )
-    for endpoint in endpoints:
-        clear = getattr(endpoint, "cache_clear", None)
-        if clear is not None:
-            clear()
-    yield
-    for endpoint in endpoints:
-        clear = getattr(endpoint, "cache_clear", None)
-        if clear is not None:
-            clear()
+    monkeypatch.setattr(profiles_routes, "_SIDEBAR_CACHE_TTL_SECONDS", 0.0)
 
 
 @pytest.fixture